The legend goes that when the people gathered to view the exhibit of Auguste and Louis Lumière, they were so afraid of the moving image of a train barreling towards them that they ran from the darkened tent in fear. So it is at the birth of a new medium, and while we doubt that personalized video will send anyone screaming from the room, there is still a sense of astonishment when your online video addresses you directly by name and tells you things that only you need to hear.

If it would surprise you to learn that the choice between eating a banana or chocolate in a lab experiment has helped to redefine the way Americans save, then you're behind on the latest thinking in "behavioral finance"—the study of how human psychology impacts investing and markets...